This line of investigation is designed to determine the effects of early malnutrition, induced by feeding rats a diet containing corn as the sole protein source, on brain serotonin metabolism and on brain functions throught to be controlled in part by serotoninergic neurons. In particular, the effect of corn malnutrition on the secretion of growth hormone and prolactin will be studied, as will the effects on the animal's sensitivity to painful stimuli. Attempts will be made to reverse any observed effects by administering L-tryptophan or diets that raise serotonin formation and levels in brain. In other studies, we will characterize the ability of the brain to transport tryptophan and other large, neutral amino acids across the blood-brain barrier in corn-malnourished rats using the tracer technique developed by Oldendorf. We will also attempt to determine why the addition of methionine to low-casein diets prevents the reduction in brain serotonin normally obtained when such diets lacking methionine are ingested chronically. The results of these studies should expand knowledge on the impact of malnutrition on specific brain compounds (here the brain neurotransmitter serotonin) and consequently on brain functions.